Alkyl sulfates typified by sodium dodecyl sulfate have frequently been used as a cleansing component of an aqueous cleanser, because of their high detergency and ability to foam large amounts. They however do not produce satisfactory feeling upon cleansing owing to lack of lubrication between hair strands. In order to overcome this, polyoxyethylene-added alkyl sulfates (alkyl ether sulfates) have come to be used popularly in view of their pleasant feeling upon cleansing. Of the alkyl ether sulfates, those with an average of 2 moles of EO have been used most typically. They are composed of about 20 wt. % of alkyl ether sulfates with 0 mole of EO, 10 wt. % or greater of those with from 1 to 3 moles of EO, and the balance of those with 4 or greater moles of EO. Alkyl ether sulfates are however much inferior in foaming speed compared with alkyl sulfates. Mixed use of an alkyl sulfate and an alkyl ether sulfate improves lathering properties a little, but cannot attain both speedy foaming and pleasant feeling of the foam.
As a technique of improving the performance of a hair shampoo composition by adjusting the composition ratio of EO-added alkyl ether sulfates which differ depending on the molar number of ethylene oxide, disclosed is an aqueous shampoo composition, which contains from 5 to 50 wt. % of a surfactant component including alkyl ether sulfates with 1 to 8 moles of ethylene oxide and an amphoteric surfactant, and less than 5 wt. % of alkyl ether sulfates with 1 mole or less of ethylene oxide (International Patent Publication No. Hei 11-507079). This shampoo composition is utterly insufficient from the viewpoint of lathering properties.
Since hair is frequently exposed to physical stimulation by daily hair care routines such as heat drying with a hair dryer and brushing, and chemical stimulation by shampooing, permanent waving, dyeing and bleaching, it is often in a damaged state with a partial component or structural loss. An oil component such as silicone oil is added to impart a shampoo composition with protecting and restoring functions. An excess amount of such an oil component, however, causes problems such as deterioration in essential performances including lathering properties and ease of finger combing through the hair upon rinsing.